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Western University astronomer says Russian meteor first of its type in more than 100 years; too small to track

The trail of a falling object is seen above the Urals city of Chelyabinsk, in this view from a residential apartment February 15, 2013. About 400 people were injured when a meteorite shot across the sky in central Russia on Friday sending fireballs crashing to Earth, smashing windows and setting off car alarms. REUTERS/Igor Lyapustin (RUSSIA - Tags: ENVIRONMENT DISASTER)

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Despite the meteor strike over Russia being the largest recorded object to hit the Earth in more than a century, it's no surprise no one saw it coming, says a member of the Western University Meteor Group.

Hundreds of people were injured and buildings damaged about 9:20 a.m. in Chelyabinsk, a city of one million about 1,500 kilometres east of Moscow.

Western University astronomy professor Margaret Campbell-Brown said the meteor was about 15 metres across, one third the size of the asteroid that flew by the Earth Friday.

Friday's larger 45-metre diameter asteroid is at the limit of what astronomers are able to track, she said.

"It doesn't surprise me at all we would miss a 15-metre object before it hits us because it would be very faint and very hard to detect," said Campbell-Brown, who is also a member of Western's Centre for Planetary Science and Exploration.

"If the object isn't lit by the glare of the sun it is hidden," she said.

The smallest object to be detected before it struck the Earth was two metres across. But it was only spotted by luck slightly less than a day before it hit in 2008.

"It was serendipitous. A telescope looking for asteroids happened to be looking in the right direction," she said.

The meteor that hit Russia produced a sonic boom when it was traveling through the atmosphere.

"We had an overpressure that was about 10% more than atmospheric pressure, which is very, very strong - big enough to shatter windows, break buildings and so on. It doesn't surprise me we had damage on this scale," Campbell-Brown said.

The last time an object of that size struck the Earth was in 1909 in Siberia. People a considerable distance from the blast were thrown to the ground and deafened, while trees closer to the impact were flattened, Campbell-Brown said.

NASA has a program, the Near Earth Object Observation (NEOO) Program, that detects and tracks comets and asteroids passing close to Earth using ground- and space-based telescopes.

The asteroid that passed close to Earth on Friday - 2012 DA14 - had nothing to do with the meteor that struck Russia earlier in the day, NASA scientists said.

'The trajectory of the Russian meteorite was significantly different than the trajectory of the asteroid 2012 DA14, making it a completely unrelated object . . . In videos of the meteor, it is seen to pass from left to right in front of the rising sun, which means it was traveling from north to south. Asteroid DA14's trajectory is in the opposite direction, from south to north," Nasa said in a statement posted on its website.